How can this person play with himself?

Why is anybody not telling how can we play ourself

Yo @Shriyan_Chess we simply have to import a game with the same name on both sides

https://en.wikipedia.org/wiki/Cyrillic_script#Letters
Just do it

U have to open another window and challenge urself

no, you have to import a game with the same names.

if u challenge yourself you play a move and when you go to other tab it looks the same

@Alancheng i know someone told me to do that but still i dont know how to do it

You can't challenge yourself

Simple:
https://lichess.org/?user=<your username>#friend
Set it to correspondence then allow lichess to send notifications to you when a move is made.
After that, just click on the notification that appears every time you move and it will take you to the opposite side to play. Repeat until you want to end the game.
That's how a game like this happened:

Or like this: